The Penglai Group in the Jiaobei Belt is the only remaining cover of the Archaean to Early Proterozoic crystalline basement in eastern Shandong. The ages of deposition of the Penglai Group and of its deformation and m...The Penglai Group in the Jiaobei Belt is the only remaining cover of the Archaean to Early Proterozoic crystalline basement in eastern Shandong. The ages of deposition of the Penglai Group and of its deformation and metamorphism have long been a subject of speculation. Whole-rock Rb-Sr ages, illite-whole-rock pair Rb-Sr ages and illite K-Ar ages recently obtained from the Penglai Group slates are reported and interpreted in this paper. On the basis of structural and metamorphic studies coupled with analyses of illite crystallinity, XRD and SEM , a whole-rock age of 473±32 Ma (Ordovician) is interpreted as the time of termination of burial metamorphism experienced by the Penglai Group. Therefore, the age of the Penghai Group is older than Ordovician. The first-phase folding and syntectonic low greenschist facies metamorphism in the Penglai Group, i.e. the Penglai Movement, took place before 299±4 Ma B.P., i.e in the Late Carboniferous. The Penglai Movement that occurred in the Jiaobei Belt on the southern margin of the North China Plate is attributed to collision between the North China and Yangtze plates along the Jiaonan Collision Belt. This demonstrates that the continent-continent collision between the North China and Yangtze plates east of the Tan-Lu Fault Zone took place in the Late Carboniferous. The collision caused N-S compression and deformation in the southern margin belt of the North China Plate north of the Qinling-Dabieshan-Jiaonan Collision Belt.展开更多
基金This study was supported by the National Natural Science Foundation of Chinathe British Overseas Development Administration and the Royal Society, U. K
文摘The Penglai Group in the Jiaobei Belt is the only remaining cover of the Archaean to Early Proterozoic crystalline basement in eastern Shandong. The ages of deposition of the Penglai Group and of its deformation and metamorphism have long been a subject of speculation. Whole-rock Rb-Sr ages, illite-whole-rock pair Rb-Sr ages and illite K-Ar ages recently obtained from the Penglai Group slates are reported and interpreted in this paper. On the basis of structural and metamorphic studies coupled with analyses of illite crystallinity, XRD and SEM , a whole-rock age of 473±32 Ma (Ordovician) is interpreted as the time of termination of burial metamorphism experienced by the Penglai Group. Therefore, the age of the Penghai Group is older than Ordovician. The first-phase folding and syntectonic low greenschist facies metamorphism in the Penglai Group, i.e. the Penglai Movement, took place before 299±4 Ma B.P., i.e in the Late Carboniferous. The Penglai Movement that occurred in the Jiaobei Belt on the southern margin of the North China Plate is attributed to collision between the North China and Yangtze plates along the Jiaonan Collision Belt. This demonstrates that the continent-continent collision between the North China and Yangtze plates east of the Tan-Lu Fault Zone took place in the Late Carboniferous. The collision caused N-S compression and deformation in the southern margin belt of the North China Plate north of the Qinling-Dabieshan-Jiaonan Collision Belt.
